use crate::error::TypeError;
use crate::semantics::{Hir, HirKind, NzEnv, TyEnv, Value};
use crate::syntax::{Const, Span};
use crate::{NormalizedExpr, ToExprOptions};

pub(crate) type Type = Value;

// A hir expression plus its inferred type.
#[derive(Debug, Clone)]
pub(crate) struct TyExpr {
    hir: Hir,
    ty: Type,
}

impl TyExpr {
    pub fn new(kind: HirKind, ty: Type, span: Span) -> Self {
        TyExpr {
            hir: Hir::new(kind, span),
            ty,
        }
    }

    pub fn span(&self) -> Span {
        self.as_hir().span()
    }
    pub fn ty(&self) -> &Type {
        &self.ty
    }
    /// Get the kind (the type of the type) of this value
    // TODO: avoid recomputing so much
    pub fn get_kind(&self, env: &TyEnv) -> Result<Option<Const>, TypeError> {
        Ok(self
            .ty()
            .to_hir(env.as_varenv())
            .typecheck(env)?
            .ty()
            .as_const())
    }

    pub fn to_hir(&self) -> Hir {
        self.as_hir().clone()
    }
    pub fn as_hir(&self) -> &Hir {
        &self.hir
    }
    /// Converts a value back to the corresponding AST expression.
    pub fn to_expr(&self, opts: ToExprOptions) -> NormalizedExpr {
        self.as_hir().to_expr(opts)
    }

    /// Eval the TyExpr. It will actually get evaluated only as needed on demand.
    pub fn eval(&self, env: impl Into<NzEnv>) -> Value {
        self.as_hir().eval(env.into())
    }
    /// Eval a closed TyExpr (i.e. without free variables). It will actually get evaluated only as
    /// needed on demand.
    pub fn eval_closed_expr(&self) -> Value {
        self.eval(NzEnv::new())
    }
    /// Eval a closed TyExpr fully and recursively;
    pub fn rec_eval_closed_expr(&self) -> Value {
        let val = self.eval_closed_expr();
        val.normalize();
        val
    }
}